1. Field of the Invention
The automated material handling system for a cargo trailer includes means to facilitate loading and unloading a cargo trailer which are integrated with automated material handling means provided on a loading dock.
2. Description of Related Art
Modern material handling systems increasingly utilize automated material handling equipment. This is particularly true in connection with automotive assembly operations. Increasingly, automotive assembly operations are utilizing what is referred to as "just-in-time" inventory control. As the term implies, this system has as an objective to delivery components to an automotive assembly plant as they are needed for assembly of vehicles. In the past, assembly plants have included large storage areas for storing large inventories of vehicle components which had been fabricated and shipped from remote manufacturing facilities. Not only does such an inventory system require that the assembly plant be provided with the storage area (which involves expensive initial construction, maintenance and utilities), such a system also requires the maintenance of a large parts and components inventory which is undesirable from a finance point of view.
However, "just-in-time" delivery of parts and components requires highly efficient assembly plant material handling techniques in order that cargo can be quickly and effectively removed from trucks and delivered to the point of use and also that empty shipping racks be removed from assembly areas and loaded onto cargo trailers in an efficient manner in view of the fact that storage space is severely limited under such a system.
One material handling system which has been in the process of implementation to achieve the desired ends above referred to involves the use of robotic lift trucks capable of moving cargo without human intervention. One useful technique involves a guidance system which operates with a combination of dead reckoning and laser guidance. This system does away with dependence on a fixed path (such as a buried wire) for robotic lift trucks. On-board computers are provided on the trucks. The trucks include sensors which work by triangulation from identifiable landmarks which are fixed in known positions within the area of operation. The landmarks are created by installing bar coded targets at convenient intervals throughout the operating area. Positions of these targets are accurately surveyed and the coordinates recorded in the system software. From information on the angle of the targets scanned, the on-board computer calculates the exact position of the vehicle by a process of triangulation.
The vehicle follows an assigned loading track. In accordance with the present invention, a similar loading track is assigned to the floor of a cargo trailer for integration into the main system. However, the restricted space available in cargo trailers, as opposed to the more roomy area available in an assembly plant, presents special problems. The present invention provides means for overcoming these problems.